全文获取类型
收费全文 | 24654篇 |
免费 | 2878篇 |
国内免费 | 1245篇 |
专业分类
耳鼻咽喉 | 68篇 |
儿科学 | 272篇 |
妇产科学 | 121篇 |
基础医学 | 3293篇 |
口腔科学 | 378篇 |
临床医学 | 1705篇 |
内科学 | 3721篇 |
皮肤病学 | 232篇 |
神经病学 | 1010篇 |
特种医学 | 441篇 |
外国民族医学 | 6篇 |
外科学 | 1416篇 |
综合类 | 4001篇 |
现状与发展 | 8篇 |
预防医学 | 1910篇 |
眼科学 | 308篇 |
药学 | 4869篇 |
13篇 | |
中国医学 | 3069篇 |
肿瘤学 | 1936篇 |
出版年
2024年 | 184篇 |
2023年 | 699篇 |
2022年 | 1370篇 |
2021年 | 1665篇 |
2020年 | 1373篇 |
2019年 | 1127篇 |
2018年 | 969篇 |
2017年 | 1027篇 |
2016年 | 1090篇 |
2015年 | 1151篇 |
2014年 | 1646篇 |
2013年 | 1934篇 |
2012年 | 1615篇 |
2011年 | 1587篇 |
2010年 | 1236篇 |
2009年 | 1100篇 |
2008年 | 1104篇 |
2007年 | 1067篇 |
2006年 | 864篇 |
2005年 | 841篇 |
2004年 | 669篇 |
2003年 | 657篇 |
2002年 | 562篇 |
2001年 | 435篇 |
2000年 | 359篇 |
1999年 | 304篇 |
1998年 | 266篇 |
1997年 | 235篇 |
1996年 | 184篇 |
1995年 | 166篇 |
1994年 | 168篇 |
1993年 | 138篇 |
1992年 | 120篇 |
1991年 | 110篇 |
1990年 | 101篇 |
1989年 | 67篇 |
1988年 | 67篇 |
1987年 | 65篇 |
1986年 | 57篇 |
1985年 | 78篇 |
1984年 | 56篇 |
1983年 | 57篇 |
1982年 | 46篇 |
1981年 | 39篇 |
1980年 | 24篇 |
1979年 | 28篇 |
1978年 | 17篇 |
1977年 | 13篇 |
1976年 | 18篇 |
1975年 | 8篇 |
排序方式: 共有10000条查询结果,搜索用时 125 毫秒
101.
低分子肝素对急性脑梗塞的影响 总被引:2,自引:0,他引:2
为了探讨低分子肝素(LMWH)在脑梗塞应用中的安全性及实用性,采用随机单盲对照方法,对39例急性脑梗塞病人,予LMWH治疗,并与低分子右旋糖酐治疗进行比较。结果显示:LMWH组对不同程度患者的神经功能恢复程度明显优于低右组(P<001),LMWH组头颅CT扫描脑梗塞体积缩小的范围比对照组明显(P<005),LMWH不减少血小板数量及纤维蛋白量,不引起出血,可改善血液流变学,降低微循环总积分值。总有效率8718%。 相似文献
102.
综述了低分子量肝素的化学和生物活性的不均一性,以及药理作用,药物动力学、临床应用等方面的差异。 相似文献
103.
人细胞色素p450IA1基因cDNA的克隆和鉴定 总被引:5,自引:1,他引:4
在用3-甲基胆蒽诱导培养人羊膜FL细胞24h后,抽提细胞总RNA并直接合成cDNA第一链。利用人工合成的一对寡核苷酸引物,采用PCR技术特异性地扩增Cyt p50IA1 cDNA。30个循环后琼脂糖凝胶电泳显示1.5Kb大小片段,长度与预计相符。Southern杂交结果证实此片段确为Cyt p450IA1 cDNA。将此片段克隆至质粒pGEM-3Z并进行部份序列分析。结果显示克隆片段包含Cyt p 相似文献
104.
French Donna L. Häglund Bert O. Himmelstein Kenneth J. Mauger John W. 《Pharmaceutical research》1995,12(10):1513-1520
Purpose. The objective of this study is to correlate drug release mechanism with measured drug concentration profiles in gel layers of Carbopol® matrices containing mesalamine or benzoic acid.
Methods. Release rate experiments with Carbopol® matrices were performed using a rotating disk apparatus. Matrices were frozen and the gel layer in the matrices was sliced using a microtome in a cryostat. Drug concentration profiles were determined by direct measurement of the concentration of the drug in the gel slices. The pH of the slices was measured using microelectrodes, and water content was measured by Karl Fisher titration.
Results. The concentration gradient in mesalamine matrices decreased over time and correlated with square root of time release rate kinetics. The concentration profiles of benzoic acid were unchanged over time and correlated with zero order release rate kinetics. Carbopol gel layers were highly hydrated (93–95% water). Gel layers in matrices with mesalamine had a more alkaline microenvironmental pH. This higher pH resulted in increased growth of the thickness of the gel layer and a reduction drug diffusivity in comparison to benzoic acid matrices.
Conclusions. The release rate kinetics of mesalamine and benzoic acid correlated to the measured concentration profiles. The shape of the concentration profiles is determined by the rate of growth of the Carbopol® gel layer and drug diffusivity. 相似文献
105.
106.
107.
C. F. POETS A. ARNING W. BERNHARD C. ACEVEDO & H. VON DER HARDT 《European journal of clinical investigation》1997,27(4):293-298
Alveolar surfactant is well known for its ability to reduce minimal surface tension at the alveolar air–liquid interface to values below 5 mN m?1. In addition, it has been suggested that surfactant is also present in the airways, particularly in the perinatal period. We isolated surfactant from pharyngeal aspirates obtained from 33 neonates immediately after delivery and analysed it for both phospholipid (PL) composition and surface tension function. PL classes and phosphatidylcholine (PC) molecular species were determined by normal and reversed-phase high-performance liquid chromatography (HPLC), respectively. Static and dynamic surface properties of the surfactant were studied in a pulsating bubble surfactometer. Sample volume was 1.3 ± 0.5 mL (mean ± SD) with a total amount of 2.5 ± 1.3 μmol of PL and a concentration of 2.1 ± 1.0 μmol mL?1 PL. HPLC analyses of PL classes revealed a composition identical with surfactant prepared from alveolar washes, i.e. PC 83.6 ± 2.1%, sphingomyelin 1.4 ± 0.5%, phosphatidylglycerol 8.1 ± 1.6%, phosphatidylethanolamine 2.1 ± 0.5% and phosphatidylinositol 2.6 ± 1.1%. Thin-layer chromatography showed almost identical results but was more time-consuming and needed more material for analysis. Analysis of PC molecular species revealed a composition typical of human alveolar surfactant with 54.7 ± 3.9% dipalmitoyl PC, 10.3 ± 1.9% palmitoyloleoyl PC and 9.1 ± 1.5% palmitoylmyristoyl PC. Minimal surface tension fell to values below 5 mN m?1 within 5 min of cycling in all subjects. The methods used in this study allowed for complete PL and surface tension analyses of surfactant obtained during routine pharyngeal suctioning after delivery at term. Whether they are also applicable to preterm neonates with respiratory distress remains to be determined. 相似文献
108.
Kathleen M. Giacomini 《Journal of pharmacokinetics and pharmacodynamics》1997,25(6):731-741
Many clinically used drugs and their metabolites as well as a variety of environmental toxins are organic cations at physiologic pH. Secretion in the renal proximal tubule constitutes a major pathway in the elimination of organic cations. In this report, the results of studies recently performed in this laboratory are presented. First, the molecular cloning of a novel splice variant of organic cation transporter from rat kidney (rOCTIA) is described. The functional characteristics of the transporter are discussed along with the implications of RNA splicing in enhancing transporter diversity. Second, the molecular cloning of the first human organic cation transporter (hOCTI) is described. Distinct interspecies differences in the tissue distribution and function of this transporter is presented. These studies have paved the way for elucidating molecular structure function relationships of organic cation transporters and for determining their physiologic role in drug absorption and elimination. The cloned transporters can be used in mammalian expression systems for screening candidate compounds identified during drug discovery and development and in the in vivo prediction of the pharmacokinetics of therapeutic agents. 相似文献
109.
Clinical and diagnostic DNA laboratories must maintain a large inventory of DNA probes for use in hybridization studies. The preparation of plasmid DNA and isolation of DNA fragments for use as probes in both expensive and time consuming. We present here a rapid and relatively inexpensive method of producing large amounts of DNA fragments from stocks, using the polymerase chain reaction (PCR). Our experience over the past year using this technique has been very positive and we believe many laboratories could benefit by employing such a labor-saving approach to maintaining DNA probes. The technique uses the bacteriophage M13 DNA sequencing primers to amplify cloned inserts contained in commonly used plasmid vectors. As examples, we illustrate the use of DNA produced in this manner as probes for linkage analysis of the fragile X syndrome and for detection of deletions in the Duchenne muscular dystrophy gene. We have also found that at least two probes can be amplified in the same PCR reaction, allowing the detection of two different restriction fragment length polymorphisms (RFLP) simultaneously. It should be possible for laboratories to devise strategies particular to their individual needs using more than one DNA probe produced in the same PCR reaction to detect RFLP's. Such strategies would need only to consider that the predicted alleles of the multiple polymorphisms do not migrate to the same position during electrophoresis. Stocks of single or multiple probes produced by the PCR could then be maintained for more rapid Southern analyses. 相似文献
110.